Drinking water safety is a major livelihood issue for thousands of households. Drinking water disinfection is an indispensable treatment for drinking water safety. The widely used chlorine disinfection process can effectively kill bacteria and viruses, but it also produces disinfection by-products (DBPs) that are harmful to human bodies. In the past forty years, carbon-containing disinfection by-products (C-DBPs) such as trichloromethane have been extensively studied and reported. However, due to the continuous growth of the world population, the rapid development of industry and agriculture, and the lack of awareness and management of environmental issues, the issue of eutrophication in global water bodies is becoming increasingly serious and China is no exception. If pollutant emissions exceed the environmental capacity of the receiving waters, the water quality of some water sources can deteriorate. The level of dissolved organic nitrogen (DON) in the water sources increases, and some DON compounds, like amino acids, etc., are so highly hydrophilic that these compounds cannot be removed by conventional water purification processes such as coagulation, sedimentation and filtration and thus react with the disinfectants (e.g., chlorine, etc.) added in subsequent disinfection processes to form nitrogen-containing disinfection by-products (N-DBPs). Studies show that the toxicity of N-DBPs is much higher than that of C-DBPs such as trichloromethane (TCM), and N-DBPs are ubiquitous in effluents after chlorine disinfection by water plants and are very unfavorable to the health of people who drink water. Therefore, N-DBPs have become one of international major research hotspots in the field of municipal administration, environment and public health nowadays.
The chlorinated N-DBPs that are currently receiving more attention include: haloacetonitriles (HANs), haloacetamides (HAcAms) and halonitromethanes (HNMs). They are often present in drinking water after chlorination disinfection (e.g., free chlorine, chloramine disinfection, etc.) at a level of μg/L. Studies show that their chronic cytotoxicity and acute genotoxicity are hundreds to thousands of times than that of THMs, thus seriously harming the health of people who drink water. The three types of halogenated N-DBPs like HANs, HNMs and HAcAms all include chlorinated, brominated and iodinated type, among which chlorinated N-DBPs have the highest concentration in drinking water after chlorination disinfection so that they are needed to be put much attention and kept in control. Chlorinated HANs include dichloroacetonitrile (DCAN) and trichloroacetonitrile (TCAN), chlorinated HAcAms include dichloroacetamide (DCAcAm) and trichloroacetamide (TCAcAm), and chlorinated HNMs include dichloronitromethane (DCNM) and trichloronitromethane (TCNM). The structures of chlorinated N-DBPs are as follows:
